The 6-foot-9 American dominated his 5-9 opponent in the first set, but Berankis fought back to take the second set, handing Isner a break in the eighth game. Isner had 10 aces in the third set, two on the final two points, and 90 percent of his first-serve points.

"I felt when the rally went past five balls, it didn't look really good for me," Isner said. "I tried to keep the points shorter, especially on my serve and I did that exceptionally well except for one game.

"I've been feeling well and I'm healthy. Nothing is bothering me and that's a good sign. I feel I'm starting to turn the corner and I'm starting to reverting to my form that I had last year at this time."

Isner will face third-seeded defending champion Juan Monaco of Argentina, a 6-1, 6-0 winner over qualifier Robby Ginepri in the late match.

"I expect another good match for sure," Isner said. "He likes to play here and he's very good on clay. He's got some great wins on clay. He's tough to beat on any surface let alone clay."

"I played better than yesterday, but I feel I can do a little bit better and I will look for that," Almagro said. "I want to get to the final, but I know that match will be tough. I need to be ready to fight for every point."

Almagro, ranked 12th in the world, used service breaks at the end of each set to beat Lorenzo.

Almagro and Lorenzo stayed on serve in the first set until the final game, when Lorenzo double-faulted to start the game and lost it at the first break point when his drop shot fell short.

They traded breaks in the second set and Almagro went into the final game with a 5-4 lead. Almagro won at the first match point with a forehand winner that left his opponent flat-footed.

The 22-year-old Williams won a tight first set after sailing through a runaway tiebreaker, but he was victimized by his serve in the second set. He rallied after falling behind 3-0 in the third set, breaking Hidalgo at the third break point in the fifth game.

Williams held and broke Hidalgo again in the seventh game when Hidalgo hit consecutive double-faults to end the game. Hidalgo escaped two match points to hold his serve in the ninth game but Williams served a love final game, ending it with consecutive aces.

"It was a really funky match with the momentum shifts," Williams said. "I was really worn out after the first set. We played some brutal points. It was an hour long, pretty physical.

"What I really need to work on to get to the next level is my fitness. Luckily, I kind of got a second wind there at the end of the third set. I kind of gave away the end of the second to get ready for the third."